RETRANSMISSION FOR ALTERNATE CROP: This artist’s rendering shows United States Magistrate, Judge John Facciola, swearing in the defendant, Libyan militant Ahmed Abu Khatallah, wearing a headphone, as his attorney Michelle Peterson looks on during a hearing at the federal U.S. District Court in Washington, Saturday, June 28, 2014. The hearing of the Libyan accused of masterminding deadly Benghazi attacks, lasted ten minutes; he pled not guilty to conspiracy Saturday at his first appearance in U.S. court. (AP Photo/Dana Verkouteren)

RETRANSMISSION FOR ALTERNATE CROP: This artist’s rendering shows United States Magistrate, Judge John Facciola, swearing in the defendant, Libyan militant Ahmed Abu Khatallah, wearing a headphone, as his attorney Michelle Peterson looks on during a hearing at the federal U.S. District Court in Washington, Saturday, June 28, 2014. The hearing of the Libyan accused of masterminding deadly Benghazi attacks, lasted ten minutes; he pled not guilty to conspiracy Saturday at his first appearance in U.S. court. (AP Photo/Dana Verkouteren)

Assistant U.S. Attorney Michael DiLorenzo, center, lead prosecutor in the federal case against Libyan militant Ahmed Abu Khattala, accused of masterminding the deadly Benghazi attacks, enters the federal U.S. District Court in Washington Saturday, June 28, 2014, with his team. (AP Photo/Jose Luis Magana)

The motorcade transporting the Libyan militant Ahmed Abu Khattala, accused of masterminding the deadly Benghazi attack at the U.S. embassy, leaves the federal U.S. District Court in Washington Saturday, June 28, 2014, after Khattala pleaded not guilty to conspiracy at his first court appearance in the United States. (AP Photo/Jose Luis Magana)

FILE – This undated file image obtained from Facebook shows Ahmed Abu Khattala, an alleged leader of the deadly 2012 attacks on Americans in Benghazi, Libya, who was captured by U.S. special forces on Sunday, June 15, 2014, on the outskirts of Benghazi. Abu Khattala was a prominent figure in the eastern city of Benghazi’s thriving circles of extremists, popular among young radicals for being among the most hard-core and uncompromising of those calling for Libya to be ruled by Islamic Shariah law. But he was always something of a lone figure. (AP Photo, File)

U.S. Marshalls monitor the area near the federal U.S. District Court in Washington, Saturday, June 28, 2014, after security at the court was heightened in anticipation of a possible court appearance by captured Libyan militant Ahmed Abu Khattala later in the day. Khatallah is one of the men accused in the deadly Benghazi attack at the U.S. embassy in Libya. He faces criminal charges in the deaths of the US ambassador to Libya and three other Americans from the Sept. 11, 2012, attack. (AP Photo/Jose Luis Magana)

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WASHINGTON (AP) â€” A court appearance for the alleged mastermind of the attacks on the U.S. mission in Benghazi, Libya, is the first step in a long legal process that could yield new insight into a fiery assault that continues to reverberate across U.S. politics.

The case of Ahmed Abu Khattala, who pleaded not guilty during a brief court appearance Saturday, also represents a high-profile test of the Obama administration’s goal of prosecuting terror suspects in civilian courts â€” even in the face of Republican critics who say such defendants aren’t entitled to the protections of the American legal system.

Abu Khattala made his first appearance in an American courtroom amid tight security, two weeks after being captured in Libya by U.S. special forces in a nighttime raid and then whisked away on a Navy ship for questioning and transport. He was flown early Saturday from the ship to a landing pad in Washington and brought to the federal courthouse, a downtown building mere blocks from the U.S. Capitol.

A grand jury indictment made public Saturday accuses Abu Khattala of participating in a conspiracy to provide material support and resources to terrorists in the attacks of Sept. 11, 2012, that killed U.S. Ambassador Chris Stevens and three other Americans. The Justice Department says it expects to bring more charges.

The Libyan who maintained a garrulous public persona at home â€” granting interviews with journalists and gaining popularity and prominence in Benghazi’s circle of extremists â€” showed little reaction during a 10-minute appearance before a federal magistrate judge. He spoke just two words, both in Arabic, in response to perfunctory questions, stared impassively for most of the hearing and sat with his hands behind his back.

He will remain in custody â€” though the judge did not say where â€” and the next court date was scheduled for Wednesday.

As the Justice Department embarks on a high-profile prosecution of the alleged militant, the case is likely to provide a public forum for new details about a burst of violence â€” on the 11th anniversary of the attacks on the Sept. 11 attacks â€” that roiled the Middle East and dominated American political discourse. In the nearly two years since the attack, dozens of congressional briefings and hearings have been held and tens of thousands of pages of documents have been released. Yet there’s still a dispute over what happened.

Republicans accused the White House, as the 2012 presidential election neared, of intentionally misleading the public about what prompted the attacks by portraying it as one of the many protests over an anti-Muslim video made in America, instead of a calculated terrorist attack. The White House said Republicans were politicizing a national tragedy.

The capture of Abu Khatalla marked the first significant breakthrough in the investigation of the attacks. Prosecutors say they hope to identify, locate and bring to court any additional co-conspirators.

“Now that Ahmed Abu Khatallah has arrived in the United States, he will face the full weight of our justice system,” Attorney General Eric Holder said in a statement Saturday. “We will prove, beyond a reasonable doubt, the defendant’s alleged role in the attack that killed four brave Americans in Benghazi.”

The Obama administration has said it’s committed to prosecuting defendants like Abu Khattala in American courts. Government officials point to successful prosecutions, like the March conviction in New York City of Osama bin Laden’s son-in-law, to suggest that the civilian justice system is fair, efficient and can yield harsh penalties for suspected terrorists.

But not everyone is convinced. Many Republicans in Congress have urged the Justice Department to send Abu Khatalla to the U.S. detention facility at Guantanamo Bay, Cuba, and say granting terrorists legal protections, such as advising them of their right to remain silent, risks hindering access to national security intelligence.

A U.S. official said Saturday that Abu Khattala had been advised of his Miranda rights at some point during his trip to the United States and continued talking after that. The official wasn’t authorized to discuss an ongoing investigation by name and spoke on condition of anonymity. The nature of those conversations wasn’t immediately clear.

The criminal case may sort out the exact role Abu Khattala is alleged to have played in the attack.

The U.S. government accuses Abu Khattala of being a member of the Ansar al-Shariah group, the powerful Islamic militia that officials believe was behind the attack.